A system for providing collision avoidance in underwater vehicles contains a spectral analysis module for determining expectation value of acoustic (incoherent) intensity. The system also contains an intercept time estimation module for: receiving continuous time series of a current incoherent acoustic intensity and low pass filtering the time series of the current incoherent acoustic intensity; estimating temporal intensity rate of change; determining an estimated time to collision for an approaching source; and performing statistical regression analysis resulting in an estimated time of potential collision and an uncertainty measure.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A system for providing collision avoidance in an autonomous underwater vehicle (AUV), comprising: a spectral analysis module for determining expectation value of acoustic (incoherent) intensity; an intercept time estimation module for: receiving continuous time series of a current incoherent acoustic intensity and low pass filtering the time series of the current incoherent acoustic intensity; estimating temporal intensity rate of change; determining an estimated time to collision for an approaching source; and performing statistical regression analysis resulting in an estimated time of potential collision and an uncertainty measure.
2. The system of claim 1 , further comprising a behavior-based autonomy module for analyzing estimated collision time and through dedicated behaviors, instructing an autonomous underwater vehicle (AUV) on which the system is located, to take evasive action.
3. The system of claim 1 , wherein the temporal intensity rate of change is estimated by use of the equation Δ = ⅆ I dB ⅆ t = ∂ I dB ∂ r ⅆ r ⅆ t = - v * ∂ I dB ∂ r = 10 v log ( 10 ) r , where r is the range of a source moving toward the underwater vehicle at speed v, and Δ is the temporal intensity change rate.
4. The system of claim 1 , wherein the estimated time to collision for an approaching source dT, is determined by use of the equation dT = r / v = 10 log ( 10 ) Δ , which states that estimated time to collision with the approaching source is inversely proportional to the time derivative of the current incoherent acoustic intensity.
5. The system of claim 1 , wherein the uncertainty measure is a standard deviation.
6. The system of claim 1 , wherein the uncertainty measure is a 95% confidence interval.
7. The system of claim 1 , further comprising a hydrophone for detecting underwater sound and a data acquisition system for digitizing analog signals received from the hydrophone and generating a digital timeseries.
8. The system of claim 2 , wherein taking evasive action is selected from the group consisting of changing depth of the AUV and having the AUV move to a safe zone.
9. The system of claim 8 , wherein the safe zone is predefined and stored within the system.
10. The system of claim 2 , wherein the AUV contains an AUV survey pattern, and wherein taking evasive action includes modifying and cropping the AUV survey pattern to contain only legs and waypoints outside of an identified no-go zone.
11. The system of claim 2 , further comprising a recognition module for recognizing spectral nature of man-made vessels and adding tonal information associated with the recognized spectral nature of man-made vessels, for consideration during taking evasive action.
12. The system of claim 1 , wherein the approaching source is a water surface craft.
13. A method of providing collision avoidance in an autonomous underwater vehicle (AUV), comprising the steps of: determining expectation value of acoustic (incoherent) intensity; receiving continuous time series of a current incoherent acoustic intensity and low pass filtering the time series of the current incoherent acoustic intensity; estimating temporal intensity rate of change; determining an estimated time to collision for an approaching source; and performing statistical regression analysis resulting in an estimated time of potential collision and an uncertainty measure.
14. The system of claim 13 , further comprising the step of analyzing estimated collision time and through dedicated behaviors, instructing an autonomous underwater vehicle (AUV) on which the method is provided, to take evasive action.
15. The method of claim 13 , wherein the temporal intensity rate of change is estimated by use of the equation Δ = ⅆ I dB ⅆ t = ∂ I dB ∂ r ⅆ r ⅆ t = - v * ∂ I dB ∂ r = 10 v log ( 10 ) r , where r is the range of a source moving toward the underwater vehicle at speed v, and Δ is the temporal intensity change rate.
16. The method of claim 13 , wherein the estimated time to collision for an approaching source dT, is determined by use of the equation dT = r / v = 10 log ( 10 ) Δ , which states that estimated time to collision with the approaching source is inversely proportional to the time derivative of the current incoherent acoustic intensity.
17. The method of claim 14 , wherein taking evasive action is selected from the group consisting of changing depth of the AUV and having the AUV move to a safe zone.
18. The method of claim 17 , wherein the safe zone is predefined and stored.
19. The method of claim 14 , wherein taking evasive action includes modifying and cropping an AUV survey pattern to contain only legs and waypoints outside of an identified no-go zone.
20. The method of claim 14 , further comprising the step of recognizing spectral nature of man-made vessels and adding tonal information associated with the recognized spectral nature of man-made vessels, for consideration during taking evasive action.
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June 28, 2012
September 9, 2014
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